Few people have ever visited the long network of underground tunnels under the public baths of Caracalla, which date back to the third century AD and are considered by many archaeologists to be the grandest public baths in Rome. This underground network, which is due to be reopened in December, is also home to a separate structure, the largest Mithraeum in the Roman Empire, according to its director Marina Piranomonte. The Mithraeum has just reopened after a year of restoration work which cost the city’s archaeological authorities around €360,000.

To celebrate the reopening, Michelangelo Pistoletto has installed his conceptual work Il Terzo Paradiso (the third heaven), which he first presented at the 2005 Venice Biennale, in the gardens surrounding the public baths. The work, made of ancient stone fragments and pieces of columns arranged in a triple loop, represents the harmonious union of the natural and technological worlds, according to the artist. It will be on view until 6 January 2013.